This invention relates to a power transfer device for providing power to the electrical system of a building, such as power supplied from a standby generator.
Portable generators are used in certain situations to feed electrical power to residential and commercial load circuits during a utility power outage. These systems frequently include a power inlet box adapted for interconnection with the generator. The power inlet box is typically mounted to the exterior of a building. The power inlet box is connected to a transfer switching mechanism which continues the electrical path through circuit breakers associated with the transfer switching mechanism, to supply power to certain selected circuits of the load center as determined by the transfer switching mechanism selector switches. The circuits of the transfer switching mechanism are wired to selected circuits of the load center, through wiring housed within a conduit extending between the load center and the transfer switching mechanism.
The present invention relates to a power transfer arrangement similar to that disclosed in Flegel U.S. Pat. No. 5,895,981 issued Apr. 20, 1999, the disclosure of which is hereby incorporated by reference. In the ""981 patent, a power transfer switching mechanism for interposition between a remote power inlet box and the electrical load center of a building includes a terminal compartment for receiving power input wires connected to the remote power inlet box. The switching mechanism includes a cabinet defining an internal cavity within which a series of switches are mounted. The cabinet further defines a terminal compartment, and a terminal assembly is disposed within the terminal compartment. The terminal compartment is accessible through an opening associated with the cabinet, and a cover is selectively positionable over the opening to provide or prevent access to the terminal compartment. A series of wires are interconnected between the terminal assembly and the switches, and power input wiring is received within the terminal compartment and interconnected with the remote power inlet box. The ends of the power input wires are engageable with the terminal assembly for establishing a direct electrical connection between the remote power inlet box and the switches of the switching mechanism.
The present invention also relates to power transfer switching mechanisms such as are disclosed in co-pending U.S. patent application Ser. No. 09/062,257 filed Apr. 17, 1998 and Ser. No. 09/139,154 filed Aug. 24, 1998, the disclosures of which are hereby incorporated by reference. The ""257 application discloses a power input terminal arrangement in the power transfer switching mechanism, in combination with a removable cover for preventing access to the power input terminal arrangement. The cover is provided with a power inlet or input structure, such as a socket or receptacle, which can be connected to the terminal assembly for selectively receiving a plug connector electrically interconnected with a source of auxiliary power such as a generator. The power transfer switching mechanism in the ""257 application provides a transfer switching mechanism which may have either a plug-type power input connection or a direct or hardwired power input connection between the remote power inlet box and the switches of the switching mechanism. The ""154 application differs from the ""257 application by disclosing a power transfer switching mechanism having a removable cover provided with a power input indicating structure, such as a pair of watt meters, which may be connected to the terminal assembly for selectively displaying the amount of power supplied to the transfer switching mechanism by the generator. In both the ""257 application and the ""157 application, a blank cover may be used in place of the cover having the power inlet or input structure of having the power input indicating structure, to provide neither plug-type power input nor power input indicating capabilities.
Co-pending application Ser. No. 09/157,855 filed Nov. 23, 1998, the disclosure of which is hereby incorporated by reference, discloses a power transfer switching mechanism having a removable cover provided with both a power inlet or input structure as well as a power input indicating structure. The power inlet or input structure may be in the form of a socket or receptacle which is adapted for connection to the terminal assembly for selectively receiving a plug connector and supplying power to the power transfer switching mechanism from a source of auxiliary power such as a generator. As discussed above, this feature provides a selective plug-type power input connection rather than a direct or hardwired power input connection between the generator and the power transfer switching mechanism. The power input indicating structure may be in the form of a pair of watt meters as discussed above, to display the amount of power supplied to the power transfer switching mechanism by the generator. The meters are also used to indicate the balance between the two output circuits of the generator and, during initial setup, to measure the total loads on each individual circuit wired into the transfer circuit. The ""855 application thus discloses a cover having a combination plug-type power input and power input indicating system which can be selectively interchanged with a blank cover.
Copending application Ser. No. 09/526,237, filed Mar. 15, 2000, discloses an arrangement generally similar to that disclosed in the ""257 application as well as the ""981 patent, but in which the power input terminal arrangement is replaced with exposed wire leads. The disclosure of the ""237 application is hereby incorporated by reference.
While the above-described power transfer switching mechanisms provide extremely convenient and simple arrangements for optionally establishing direct, hardwired and selective plug-type connections with the generator or power inlet box and for optionally pending power input monitoring capability, it is desirable to provide a power transfer switching mechanism which can be quickly and easily equipped with a power input receptacle and/or a meter arrangement, or which can be constructed without either a power input receptacle or a meter arrangement. With this modification, the transfer switching mechanism can be configured to receive a power input plug interconnected with the generator if desired, or can be configured to provide a direct, hardwired connection with a remote power inlet. The transfer switching mechanism can also be selectively configured to enable monitoring of the amount of power provided by the generator during a power outage, so as to prevent overloading of and subsequent damage to the generator or to the building electrical system. Although the broad concepts of integrally providing a power input receptacle and meters on a power transfer switching mechanism are well-known, it is desirable to modify the power transfer switching mechanisms described in the aforementioned patents and patent applications, to provide an optional power input and meter arrangement in a cover assembly which can be selectively engaged with the cabinet of the transfer switching mechanism.
It is an object of the present invention to provide a transfer switching mechanism having a selectively engageable access cover arrangement capable of providing the transfer switching mechanism with a power input arrangement, a meter arrangement, a combination power input arrangement and meter arrangement, or without either a power input arrangement or a meter arrangement, according to the desired configuration and intended use of the transfer switching mechanism. It is a further object of the present invention to provide such a transfer switching mechanism which is generally similar in construction and operation to known transfer switching mechanisms. It is a further object of the present invention to provide a method for efficiently constructing a power transfer switching mechanism having interchangeable access covers for providing desired functions such as a receptacle-type power input for supplying power from the generator, and a meter panel for monitoring power input from the generators. Yet another object of the invention is to provide such a transfer switching mechanism in which a power input or meter arrangement can be installed or removed at the time of manufacture or at the time of field installation, or retrofitted at a time after installation, at the discretion of the installer or user.
In accordance with the invention, a power transfer arrangement is adapted for interconnection in the building electrical system for supplying power from a generator to the electrical system. The power transfer arrangement includes a power inlet arrangement for interconnection with the generator for receiving power therefrom, and a power transfer device separate from the power inlet arrangement adapted for interconnection with the building electrical system. The invention resides in a power input connection arrangement, such as a terminal arrangement or exposed wire leads in the power transfer device, in combination with a selectively configurable cover system adapted for engagement with the power transfer device for preventing access to the power input connection arrangement. In one form, the power transfer device includes a cabinet having a panel to which is mounted a set of switches for controlling the supply of power from the power transfer device to the building electrical system, and the set of switches are electrically connected to the power input connection arrangement. The power input connection arrangement may be in the form of a set of power input terminals or exposed wire leads located within a power input compartment defined by the cabinet at a location spaced from the set of switches. The cabinet defines an open area which provides access to the power terminal compartment.
The cover system according to the invention contemplates a pair of separate cover members or sections which are selectively engageable with the power transfer device over the open area of the power transfer device cabinet, for selectively preventing access to the power input compartments. Each cover member or section is engageable with the power transfer device cabinet separately from the other, and the cover members or sections cooperate to enclose the open area of the power transfer device cabinet when the cover members or sections are engaged with the power transfer device cabinet.
The cover members or sections may be blank, having nothing more than mounting structure and wall structure which cooperate to mount the cover section to the cabinet and enclose a portion of the open area, or the cover sections may carry certain components useful in operation of the power transfer device, such as a power input member in the form of a socket or a receptacle, or a power input indicating arrangement such as a power meter. The invention contemplates that the pair of cover members or sections which are mounted to the cabinet may be selected from a group of cover sections which includes first, second and third differently configured cover sections. Representatively, each of the first cover sections includes a power input arrangement, each of the second cover sections includes a power input indicating arrangement, and each of the third cover sections is a blank cover section. The pair of cover sections which are selected for mounting to the cabinet over the open area are selected according to the design parameters or operating characteristics of the power transfer device.
In one version, a pair of third (blank) cover sections may be selected and mounted to the cabinet over the open area, when it is not desired to provide the power transfer device with either a power input socket or receptacle, or with a power input indicating arrangement. In this version, power is typically supplied to the power transfer device from the generator by wiring a remote power inlet directly to the set of wire leads or terminals contained within the power input compartment, and the blank cover sections simply allow access to the set of wire leads or terminals for establishing the direct connection, and enclose the open area so as to prevent access to the power input compartment after the direct connection has been made.
In another version, the selected pair of cover sections include a third (blank) cover section and a first cover section, which includes a power input arrangement. In this version, the power input arrangement, typically a socket or receptacle, is wired to the set of wire leads or terminals and the first cover section is mounted to the cabinet so as to enclose a portion of the open area. The third (blank) cover section is mounted to the cabinet so as to enclose the remainder of the open area. This version is employed when it is desired to provide a plug-type connection to supply power from the generator to the power transfer device.
In another version, the selected pair of cover sections include a third (blank) cover section and a second cover section, which includes a power input indicating arrangement such as a meter. In this version, the meter is interconnected with the set of wire leads or terminals or with the power input wiring from the remote power inlet arrangement, and the second cover section is mounted to the cabinet so as to enclose a portion of the open area. The third (blank) cover section is mounted to the cabinet to enclose the remainder of the open area. This version is employed when it is desired to provide the capability to monitor power supplied to the power transfer device by the generator.
In yet another version, the selected pair of cover sections include a first cover section and a second cover section, to provide both power input and power indicating capability. In this version, the power input arrangement, such as the socket or receptacle, is wired either to the meter or to the set of wire leads or terminals, and the meter is then wired to the set of terminals or is otherwise interconnected with the power input wiring. In a construction in which the power input socket or receptacle is wired to the wire leads or terminals, a power sensor such as a current transformer is interconnected with the meter and is positioned so as to detect current in the wiring which extends between the power input socket or receptacle and the set of wire leads or terminals. In a construction in which the socket or receptacle is connected to the meter, wires from the meter are then connected to the set of wire leads or terminals for inputting power to the power transfer device from the socket or receptacle through the meter. When mounted to the cabinet, the first and second cover sections cooperate to enclose the open area to prevent access to the power input compartment.
With this arrangement, the cover structure of the power transfer device can be varied to provide different functions and operating characteristics for the same basic construction of the power transfer device. That is, a common set of power transfer device components can form the basis for constructing a power transfer device having different functions and characteristics, according to the cover sections which are selected and mounted to the base components of the power transfer device.
The invention also contemplates a method of constructing a power transfer device, substantially in accordance with the foregoing summary.